Amelioration of aluminum toxicity on OM4900 rice seedlings by sodium silicate

Abstract

Silicon has versatile functions in plant biology, especially in plant defense and tolerance to both biotic and abiotic stressors. In this study, it was investigated if silicon could reduce the toxic effect of aluminum on rice. Aluminum was applied to OM4900 rice seedlings, and then their growth and sugar metabolism were determined. At doses of aluminum chloride of 100 and 200 µM, plant height was significantly enhanced and root elongation was reduced. The accumulation of photosynthetic pigments was tightly correlated with the aluminum concentration showing highest amounts at 400 µM. Sugar levels in roots and endosperm decreased upon aluminum addition. Aluminum toxicity in rice seedlings was relieved by addition of silicon in the form of sodium silicate. In the presence of 200 µM aluminum chloride, the addition of 100 mg/L sodium silicate to the hydroponic solution showed no contribution to plant growth or buildup of photosynthetic pigments. At this concentration, root development was not affected while it was at higher concentrations. Sodium silicate addition did not alter the reduction in sugar levels by aluminum. The presence of 200 µM aluminum chloride with or without sodium silicate in the growing solution significantly decreased silicon content in rice husks.   Key words: Cultivar, metal, root, silicon, sugar.